The present invention relates to a tile-like ceramic element which is provided on its visible side with an electrically conductive surface glaze which, when the tile-like ceramic element is laid together with a plurality of such elements to form a covering for lining walls or floors, communicates with an electrically diverting substructure to be provided below the covering. Coverings made of such tiles are used, for example, as flooring for operating rooms, laboratories, industrial rooms with a fire risk such as paint shops, paint factories, storehouses for inflammable solvents, etc. They have also started to be used in areas where a noticeable discharge on persons is to be avoided, for example in office rooms in which computers and similar electrical and electronic devices are set up.
Flooring in operating rooms and the like is required to ensure constant diversion of static electricity and, at the same time, to prevent current from flowing off at a dangerous strength when there is contact between a human body and poorly insulated current-carrying parts. This generally means that the flooring must have an electrical resistance in the range of 10.sup.4 to 10.sup.6 ohms.
The flooring made of PVC and other synthetic materials as used up to now suffers from the fact that its resistance to organic solvents and other chemicals leaves much to be desired. Furthermore, such flooring must be connected to the floor by electrically conductive adhesives which are not stable for long periods in terms of their conductivity.
Use has, therefore, begun to be made of ceramic floor tiles produced by firing molded mixtures of stoneware clay or potter's clay and iron oxide in an atmosphere customary for firing floor tiles. German "auslegeschrift" No. 17 71 361 might be stated as an example of a method of producing such electrically semiconductive ceramic floor tiles. However, the admixture of iron oxides to the ceramic material causes darkly colored unglazed ceramic surfaces to be obtained. Furthermore the band width of the conductivity of such floor tiles made to be electrically conductive is insufficient.
In "Baukeramik" 8/84, p. 96, the Villeroy & Boch Company presents a new grayish-blue conductive tile with a 15.times.15 cm format, consisting, in the practical, commercially available embodiment, of a ceramic tile having an electrically conductive coating drawn over the side edges. Thus, electricity can be diverted only via the joint material adjacent to the edges of such tiles, which generally consists of material bound with cement made to be electrically conductive. However, this joint material is subject to aftercontraction so that the electrical contact with the side edges of the tiles can disappear at least in part. Furthermore, this joint material is washed out very quickly in view of the cleaning which must be performed extremely often, in particular in operating rooms, which also leads to a reduction of the contact surfaces. Thus, not only does the leakage resistance vary, the mechanical loading capacity of the tile covering also suffers. Furthermore, when the joint material contracts or is worn away, this gives rise to tiny spaces that may fill with germs between the tile edges and the joint material, which is absolutely intolerable in operating rooms. As the cited publication shows, the tiles have a relatively small format so that the on-side transition resistance required by the test standard (VDE Regulation 0100/5.73 Art. 24) can only be reached by the joint portion.